Impact of Global Warming
Earth has a remarkably moderate and stable climate that is just suitable for the flourishing of life on this planet. Nonetheless, in its billions of years of geological history, the planet has seen considerable fluctuations in its climate, presenting hostile climatic conditions to many of its inhabitants for long stretches of time.
Earth has seen many extinction events in its long history, but the greatest of them was the Permian-Triassic extinction event that happened 251 million years ago when over 90% of the living species perished. One of the major hypotheses advanced to explain this catastrophe was a runaway greenhouse effect caused by increased volcanism and / or abrupt release of methane hydrates from the ocean floor, methane being a powerful greenhouse gas. Though such extreme climatic events were rare, warming and cooling cycles keep recurring on the planet. For example, there have been many long spells of ice ages in the past, and these deep freezes will continue occurring on the planet in future.
In the past few decades, the average temperature of the earth has risen by about 1°C. Such fluctuations in earth’s temperature have not been uncommon in the historical continuum of the human civilization itself. If the current global warming is happening in the natural course of things, there are good chances for it to stabilize by itself, as a part of the recurring climatic cycles of the planet. But if it is human-caused its intensity can go on increasing in a linear fashion and wreak unimaginable havoc everywhere on the planet. The earth’s fragile and complex climatic system would go awry.
In general, the global climatic system is highly resilient and the earth’s atmosphere as a whole may be too vast to be impacted by the side effects of human activities, notwithstanding the obvious and undeniable harm caused by pollution at a local level. Nevertheless, whether caused by humans or not, global warming is inherently a very dangerous phenomenon that is always likely to start a positive feedback loop that could go out of control. A positive feedback loop is a vicious circle where rising temperatures of the planet changes the environment in such a way that these changes bring about a further increase in the earth’s temperature. Consequentially it becomes a runaway effect. Civilization-threatening cataclysmic upheavals in the earth’s climate system are expected if such positive loops were to occur in the next several decades.
Global warming could melt the Greenland and Antarctic ice sheets away, which could result in the flooding of coastal areas all over the globe. Further, there are fears that massive inputs of fresh water from the polar ice shelves into the Atlantic Ocean will shut down the Atlantic Gulf Stream which is responsible for regulating temperatures in many parts of Europe and America. If this happens, it could even trigger the onset of a new Ice Age. Further on, if the sea-levels continued to rise unimpeded, it could eventually lead to a global deluge. A doomsday scenario is not unlikely — but how much time we have before the worst could happen?
In 2001, the IPCC (Intergovernmental Panel on Climate Change) brought out an alarming report documenting the present state and the possible fate of the planet earth. According to projections made in that report, the temperature of the planet can rise anywhere between 1.4 degrees and 5.8 degrees over the next hundred years or so. Assuming that the average temperature of earth rose by 6 degrees, the question is: would it continue to rise further thereafter? But this question may be irrelevant because if the temperature rose by 6 degrees it could already spell doom for the planet and all its inhabitants. A six-degree rise in temperature might not sound like much, but it could seal the fate of the planet, destroying much of the life on it and reshaping our physical world beyond recognition.
At a one degree increase, most coral reefs and a large number of mountain glaciers of the planet would have been lost.
Two degrees will complete the melting of the Greenland ice sheet, which could possibly raise global sea levels by as much as seven meters. Seven meters may sound extreme — since going by mainstream predictions the global sea-levels are expected to rise only by 50 or 100 centimeters by the end of the century — but it is very much within the realm of possibility. And this could happen not after a hundred years but just after 20 to 30 years from now. A third of all species alive today could have been driven to extinction even as their habitats and ecosystems are wiped out (Lynas, 2007).
At a three degree rise, millions of square kilometers of Amazon rainforest would have nearly vanished, with vast regions of land in Midwestern United States and southern Africa turning into deserts. A three-degree rise could be a very critical one, since it could be a tipping point — where the phenomenon of global warming would go out of control, leaving us completely helpless victims of the ceaseless climatic changes. So many countries across the world could become uninhabitable because of the extreme drought and heat conditions. Agriculture would be seriously affected. Tens of millions of people could become climate refugees. Hurricanes would dramatically increase in frequency, with half of them blowing at Category Five speeds. The number of climate refugees could slowly escalate to hundreds of millions or even billions. Essentially, the social and economic situation of the world would be in shambles.
At four degrees, another major positive feedback loop would set in with the release of billons of tons of carbon dioxide and methane gas that is now locked up in Arctic permafrost. The effects of this process are essentially unpredictable. The whole Arctic ice cap would have vanished. Polar bears and other Arctic species would have been long extinct. In the South Pole, the Western Antarctic ice sheet could collapse into the warming ocean waters and melt away rapidly, leading to another 5 meter increase in global sea levels. Most of the smaller island nations would have submerged into the ocean. The summer temperature in Switzerland may reach 48 degree centigrade. Alps would be completely stripped of the snow layer.
At five degrees, the Earth could resemble the way it was during certain periods in geological time which experienced extreme global warming. For example, 55 million years ago, in the Eocene, the release of methane hydrates from the ocean bed caused a long spell of intense global warming. Vast amount of methane hydrates are still embedded in the continental shelves below the ocean. These reserves could become unstable at higher temperatures and would be released out. If this happens the world is not far from seeing an apocalyptic scenario. With a five degree rise in temperature, the release of methane hydrates is at least likely to happen in shallower seas of the world. In the Eocene, the greenhouse effect intensified very gradually, over a period of 10,000 years, but it could happen in the near future now, in less than ten decades.
At six degrees, the earth will resemble the way it was at the end of the Permian period, 251 million years ago. Most of life on the earth would have gone. Humanity could have survived all the catastrophes, but civilization would be a thing of the past — that civilization which in all probability brought about this disaster upon itself and the entire world in the first place. Earth may regain its balance after several thousands or even millions of years, just like it did many times in the past. But we would not be around to experience and enjoy the pristine life-giving natural climate once again on this planet.
Lynas, M. (2007). ‘Six steps to hell’ – summary of Six Degrees as published in the Guardian.
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